1. Field of the Invention
This invention relates to flexible mastic, coating, and caulk compositions.
2. Description of the Prior Art
Mastics, coatings, and caulk compositions which are designed to remain flexible when cured usually require long periods of time to achieve tack-free properties. This is a problem in many applications; for example, with roof mastics which coat a roof which has previously been coated with a foam, the workers cannot walk on the roof until it becomes tack-free. Although non-flexible, quick tack-free compositions have been provided by others, no one has provided a flexible composition of low Tg which becomes tack-free upon exposure to air as is provided by the present invention. More specifically, others have provided flexible low Tg early tack-free compositions based either on aqueous emulsions, solvent solutions of cured polymers, moisture-cure systems, or reactive systems. The aqueous systems are disadvantageous in that they will not cure well under low temperatures or high humidity. Solvent solutions of cured polymers are disadvantageous in that a large quantity of solvent is used and all of it must evaporate for the system to function. The loss of the solvent is expensive and causes pollution. Moisture-cure systems are disadvantageous in that they are slow and do not cure well under dry conditions. Reactive systems which are two-part compositions are disadvantageous in that they must be mixed and applied shortly after mixing, and that they cannot be stored for a long time after mixing.
German Offenlegungsschrift No. 2,025410, published Dec. 9, 1971, shows compositions comprising unsaturated polyesters which are crosslinked with monounsaturated monomer such as styrene in the presence of an accelerator system comprised of a vanadium compound and thioglycolic ester of at least trihydryic polyols. The composition is said to cure and dry more rapidly than with the use of monohydric thioglycolates, giving tack-free surfaces after complete hardening. At least 20 parts monomer per 80 parts unsaturated polyester is required, and no low T.sub.g polymers which are flexible on cure are taught.
Hofer et al U.S. Pat. No. 3,516,976 shows vinyl monomers which are acrylic acid esters or methacrylic acid esters, for example, methyl acrylate or methylmethacrylate, polymerized by a redox system comprised of an organic vanadium compound and a linear aliphatic primary mercaptan.
Kehr U.S. Pat. Nos. 3,662,023 and 3,697,397 show liquid polyenes having at least two terminal unsaturated groups and a polythiol having multiple pendant or terminal SH groups which crosslinks or cures the polyenes to solid resins or elastomers.
Other prior art which has been considered but is thought to be less relevant are GER DT No. 1,912,426 (Rohm GmbH); U.S. Pat. No. 3,333,021 (Electrochemische Werke); Japanese 71/38710 (Johoku); DL 121,524 (Waibunger University); EP 34,118 (Ceiba Geigy); and U.S. Pat. No. 4,120,721 (W. R. Grace).
It is an object of the present invention to provide soft flexible polymer compositions which become substantially tack-free within a short time at ambient conditions. A further object is to provide elastomeric coatings, caulks, and sealant compositions which are soft, have a low T.sub.g, and cure under ambient conditions to obtain a flexible film substantially free from tackiness. A still further object is to provide stable one package compositions which form flexible films which cure upon exposure to ambient air and become tack-free quickly.